1. Field of the Invention
The invention is related to the field of communications and, in particular, to providing third party charging for SIP sessions or SIP transactions in communication networks, such as IMS networks.
2. Statement of the Problem
One type of communication network gaining popularity is an IP Multimedia Subsystem (IMS) network. As set forth in the 3rd Generation Partnership Project (3GPP) or 3GPP2, IMS provides a common core network having access-agnostic network architecture for converged networks. Service providers are accepting this architecture in next generation network evolution. The IMS architecture is initially defined by the 3GPP to provide multimedia services to mobile subscribers over an Internet Protocol (IP) network. IP networks have become the most cost savings bearer network to transmit video, voice, and data. IMS uses the advantage of IP networks to provide multimedia services for IMS subscribers on an IMS platform. The signaling used within IMS networks is Session Initiation Protocol (SIP). IMS defines the standard SIP interface between application servers, the IMS core network (CSCF), the IMS subscriber, the IMS database (HSS), and IMS billing elements. These standards can reduce the network integration costs and let the subscriber enjoy more stable services.
One problem with present IMS networks is that the offline charging mechanism defined by the 3GPP standards only includes information about the calling party and the called party to indicate who should be charged for a session. The 3GPP standards do not describe how to indicate that a call should be charged to a party other than the calling party or the called party. In some circumstances, it may be desirable to charge other parties to the call, such as calling card calls, credit card calls, a forwarded or transferred call, etc. The present standards do not provide such a mechanism.